XTL5000 2.85v regulator issue
Posted: Sun Jul 16, 2017 4:41 am
Any component level XTL techs out there?
I have a couple VHF main boards that were fried by connecting a bad O5 head to them. Being VHF, I'd really like to fix them.
At first I thought it was an sb9600 bus issue, but when I found sb9600_enable was not even turning on I looked elsewhere.
I am finding the 2.85v regulator at about 1.3 volts. It's not the regulator chip, I replaced that same result. The other regulators are also low, but since they are enabled by the 2.85 vcc that is understandable.
5v is good by the way. Filtered 5v is low but that is due to current draw from 2.85v regulator through a dropping resistor I think.
2.85 vcc goes lots of places. Short of unsoldering every 2.85 vcc chip lead, how can I troubleshoot this?
Another thing that puzzles me is I measure about 5k ohms on the 2.85 vcc both on the bad radio and on a good radio. I would have expected it to be lower on the bad radio but it is the same.
Something is not letting the 2.85 come up, and that kills everything else down the line.
Head says fail 01/90 btw.
Thanks for any ideas.
I have a couple VHF main boards that were fried by connecting a bad O5 head to them. Being VHF, I'd really like to fix them.
At first I thought it was an sb9600 bus issue, but when I found sb9600_enable was not even turning on I looked elsewhere.
I am finding the 2.85v regulator at about 1.3 volts. It's not the regulator chip, I replaced that same result. The other regulators are also low, but since they are enabled by the 2.85 vcc that is understandable.
5v is good by the way. Filtered 5v is low but that is due to current draw from 2.85v regulator through a dropping resistor I think.
2.85 vcc goes lots of places. Short of unsoldering every 2.85 vcc chip lead, how can I troubleshoot this?
Another thing that puzzles me is I measure about 5k ohms on the 2.85 vcc both on the bad radio and on a good radio. I would have expected it to be lower on the bad radio but it is the same.
Something is not letting the 2.85 come up, and that kills everything else down the line.
Head says fail 01/90 btw.
Thanks for any ideas.